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    <title>Document</title>
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<script>

let a = 'nihaonihaob'

function getStr (str) {
    for (let i = 0; i < str.length; i++) {
        let k = str.indexOf(str[i])
        let index = str.indexOf(str[i], k+1)
        if (index === -1) {
            return {
                index: i,
                value: str[i]
            }
        }
    }
    return -1
}

console.log(getStr(a))




</script>
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